Speaker enclosure



Oct. 23, 1962 D. ARDEN 3,059,719

SPEAKER ENCLOSURE Filed Nov. 17, 1958 'Il le 11V, 2e le S M Il s 42 .Il .30 32 'e INVENTOR.

DAVID ARDEN United States Patent O 3,059,719 SPEAKER EN CLOSURE David Arden, 4337 Fairmont, San Diego, Calif. Filed Nov. 17, 1958, Ser. No. 774,325 6 Claims. (Cl. 181-31) The present invention relates generally to sound reproduction ydevices and more particularly to a speaker enclosure.

The primary object of this invention is to provide a speaker enclosure -for use with conventional loudspeakers land having a novel type of pressure damping plug resiliently mounted in the back panel of the enclosure which prevents undue bass response pressure peaks inside the enclosure.

Another object of this invention is to provide a speaker enclosure in which the plug is mounted on a simple sus- -pension structure which ensures accurate alignment and free movement of the plug.

A further object of this invention is to provide a speaker enclosure in which the plug suspension means is adjustable to control the bass response frequency within certain limits.

Another object of this invention is to provide -a plug structure which is adaptable to many types of enclosures and for use with many different speakers.

Another object of `this invention is to provide a speaker enclosure which is practicable and inexpensive to manufacture.

Finally, it is an object to provide -a speaker enclosure of the -aforement-ioned character which is simple and convenient to construct and use and which will give generally efficient and durable service.

With these and other objects `definitely in view, this invention consists in the novel construction, combination and arrangement of elements and por-tions, as will be khereinafter fully described in the specification, particularly pointed out in .the claims, and illustrated in the ,drawing which forms a material part of this disclosure,

and in which:

FIGURE 1 is a side elevation View, partially cut away,

vof a speaker enclosure with the plug structure installed;

FIGURE 2 is an enlarged fragmentary view of the inner face of the enclosure back panel taken in the direction of arrows 2 2;

-FIGURE 3 is a sectional view taken on the line 3 3 of FIGURE 2; and

FIGURE 4 is a sectional view similar to FIGURE 3, showing an alternative structure.

Similar characters of reference indicate similar or identical elements and portions throughout the specification and throughout the views of the drawing.

Referring now Ito the drawing in detail, the enclosure Iis of conventional construction, having a front panel 12 on which the speaker 14 is mounted and a back panel 16. The structure of the enclosure 10 is rigid and securely put together in Ian approved manner to withstand the pressure and vibration Iimposed by full volume output from the speaker 14. In the rear panel 16, substantially in axial alignment with the speaker 14, is an opening 1S, of an area very small in relation to the area of the rear panel, ordinarily but not necessarily circular, in which is mounted a correspondingly shaped plug Ztl of lightweight material -such as cork, `or the like, said plug having sufficient clearance to move freely in an axial direction within said opening. However, the plug 20 may be mounted in another portion of the enclosure 10 according to the installation. The plug `20 is xed t0 a pair of resilient suspension bands 22 and 24 arranged in the form of -a cross and intersecting in overlapping relation at the axis of said plug, said bands being of rubber or the like and cemented or otherwise secured to each other and -to the plug. The ends of the suspension bands 22 and 24 are fixed to support blocks 26 secured to the inside of the back panel 16 and equally spaced radially of the opening 18. The thickness of the support blocks 26 is such that the plug 2t) is held with its outer end 28 protruding slightly outside the back panel 16, as in FIG- URE 3. The suspension bands 22 and 24 are slightly tensioned to eliminate slack and ensure that the plug 20 is held coaxially with the opening 18 for free movement.

Adjacent each support block 26 is an adjusting screw 30 threaded through a nut plate 32 secured on lthe back panel 16, the head of said screw tting into a suitable socket 34 in said back panel. Attached to the inner ends of the adjusting screws 30 are small pads 36 which can be brought to bear on the suspension bands 22 -and 24 adjacent their support blocks. Thus by screwing in the `adjusting screws 30, the suspension bands 22 and 2.4 can be stretched and their tension increased, las indicated in dash line in FIGURE 3. In this manner the natural vibration frequency of the plug 20 can be adjusted. It will be evident that the suspension bands 22 and 24 may be replaced by other resilient material such as steel springs or the like.

Alternatively, the vibration of the plug may be controlled by changing its mass, as in the structure illustrated in FIGURE 4, in which a plug 40 is suspended on a single flat leaf spring 42 fixed to a block 44 on the panel 16. The plug 40 has an internal screw threaded socket 46 ex- -tending axially inwardly from the rear face 48, said socket containing an interchangeable ballast 'weight 50 screw threaded therein. By using ballast weights of different sizes, the mass of the plug 40 can be changed to suit and Ithe speaker output can be balanced to the acoustics of the particular room.

Conventional speaker enclosures of the high-fidelity -type are usually of large dimensions, compared to the speaker size, in order to contain a large air column. When the speaker produces low tones in the bass register,

ice

Vthe speaker cone has a greater travel than when producing high tones. If the speaker cone is completely free, ex

tremely low tones cause excessive cone ltravel, resulting in distortion Iand possible damage to the speaker. But the large volume of air in the conventional enclosure is restricted in its escape and provides a damping effect on the speaker cone, while still allowing true reproduction of the sound. The bass reproduction capabilities of a speaker are largely controlled by the size of the enclosurev and the air column contained therein, and the size of some extended range units is unwieldly. On the other hand, reducing the size of the enclosure has heretofore resulted in greater damping effect and cutting out a portion of the low range reproduction.

-It has been found in tests that :the resilient plug assembly described herein enables a small enclosure to be used with a particular speaker, yet the bass response is comparable to that produced from a much larger conventional enclosure. Excessive movement of the speaker cone causes pressure uctuations lof the air in the enclosure 10. Pressure above a cer-tain predetermined value forces the plug 20 outwardly against the action of Ithe resilient suspension bands 22 and 24, the plug bouncing in an axial direction in the opening 18 in Iaccordance with the pressure uctuations and providing a damping effect. It should be noted that the gap between the plug 20 and the opening 18 is constant and -is not a variable air leak, the buffer effect of -the movable plug providing `all the pressure relief. By adjustment of the screws 30, the suspension band tension may be changed so that a different pressure peak is required to move the plug. Thus the plug can be effectively tuned to a particular low frequency range to suit an individual speaker. A similar ltuning effect is obtained by use of different ballast weights 50 in the plug 40. The structure may be applied to single or multiple speaker installations in various types of enclosures, the simple arrangement shown being but one example.

'The operation of this invention will be clearly comprehended from a consideration of the foregoing description of the mechanical details thereof, taken in connection with the drawing and the above recited objects. It will be obvious that all said objects are amply achieved by this invention.

It is understood that minor variation from the form of the invention disclosed herein may be made without departure from the spirit and scope of the invention, and that the specification and drawing are to be considered as merely illustrative rather than limiting.

I claim:

l. A speaker enclosure comprising:

a first panel having an opening therein;

a vsecond panel having an opening for mounting a speaker therein, said speaker opening in said second panel being appreciably larger than said opening in said rst panel;

a cylindrical plug having a cross section corresponding to, and slightly smaller than that of said opening in said first panel to provide a close t between the outer surface of said cylindrical plug and the inner surface of said opening of said first panel; and

resilient means for positioning said cylindrical plug in said opening in said first panel with the longitudinal `axis of said cylindrical plug coincident with the longitudinal axis of said opening in said first panel, whereby air pressure produced by the movement of said speaker causes said plug to move axially in said opening.

2. A speaker enclosure comprising:

la rst panel having a circular opening therethrough;

a second panel having an opening therethrough for mounting a speaker, said speaker opening in said second panel being at least four times the opening in `said irst panel;

a cylindrical plug having a circular cross section corresponding to, and slightly smaller, than that of said circular opening in said iirst panel to provide a close t between the outer surface of said circular cylindrical plug and Ithe inner surface of said circular opening of said rst panel; and

resilient means for positioning said circular cylindrical plug in said circular opening in said rst panel with the longitudinal axis of said circular cyl-indrical plug coincident with the longitudinal axis of said circular opening in said -irst panel, so that the air pressure produced by the movement of `said speaker causes :said circular cylindrical plug to move relative to said circular opening without unplugging said opening.

3. A speaker enclosure comprising:

a iirst panel having an opening for mounting a speaker;

a second panel having a circular aperture of a diameter smaller than one-fourth that of said speaker open- 5 a cylindrical circular plug of lightweight material having an axial length appreciably greater than the thickness of said second panel, and having a diameter slightly smaller than that of said circular aperture to dene a lclose fit between the convex surface of said circular plug and the concave `surface of said circular aperture; and

resilient means for positioning said plug in said aperture with their axes coincident and with the ends of said cylindrical plug extending beyond respective surfaces of said second panel to permit said plug to have a longitudinal vibratory movement in said aperture so that said plug does not unplug, and does not seal said aperture.

4. The combination of claim 3 wherein -said resilient positioning means comprises:

`four support blocks affixed to the inner surface of said second panel, and positioned symmetrically with respect to said circular aperture;

a single pair of resilient suspension bands, each band having respective ends thereof affixed to diametrically opposite said support blocks to form a cross having its overlapping portion at the axis of said aperture; and

means for aflixing :one end of said cylindrical plug to said bands at said `overlapping portion so that the axes of said plug and aperture are coincident and the ends of said cylindrical plug extend beyond the respective surfaces of said second panel.

5. The combination of claim 3.wherein -said resilient 35 positioning means comprises:

a single leaf spring; means for attaching one end of said cylindrical plug to one end of said leaf spring; means -for attaching the other end of said leaf spring to the inner surface of said second panel, so that the taxis of said cylindrical plug is coincident with the axis of said aperture, and the ends of said cylindrical plug extend beyond respective surfaces of said lsecond panel.

6. The combination of claim 3 wherein said cylindrical plug comprises an internal screw-threaded socket extending axially inward from the end of the plug that extends beyond the outer surface of said second panel so that replaceable ballast weights of selected mass may be readily screwed into and out of said screw-threaded socket.

References Cited in the le of this patent UNITED STATES PATENTS 2,713,396 Tavares Iuly 19, 1955 

